It is previously known to correct or compensate for deficiencies and manufacturing variations in a given member which forms part of a system. The member can, for example, be manufactured with greater tolerance accuracy or be made to cooperate with incorporated or connected compensating devices which compensate for changes in, for example, temperature. In cases where the system requires rapid functioning of the first member and the latter operates with a comparatively great inertia, it is previously known to arrange for the first member to be controlled such that it is acted upon in advance in order to compensate for the inertia. It is also previously known, with communication protocols which operate with well-defined time transmission of signals and in similar arrangements, to use a message system in which the messages are numbered and transmitted in a predetermined order, for example in an order which corresponds to the message numbering.
In systems of the above type, there is often a significant requirement to achieve very accurate operation of the system. This is made difficult by the fact that components incorporated in the system are sensitive to external and internal factors which result in their dependence upon manufacturing tolerances, exchange of brand, temperatures or other factors. It is also a great advantage for the system to have a structure which comprise technically simple and economically advantageous components. The last-mentioned requirements conflict with the requirement for great system accuracy, since such accuracy presupposes accurately manufactured components which are incorporated in a non-critical cooperating function in the system.
The present invention proposes a device and a method which solve, among other things, the abovementioned problems. By means of the invention, the mechanical deficiencies of the components involved can be compensated by a system function which is built into a software used. This can be designed so that the mechanical deficiencies are easily compensated.
In systems of the relevant type, there are also difficulties in generating and transmitting the signalling from the second member to the first member so that clear function executions are obtained from the first member. It is desirable to use and deal with information from a non-intelligent pulse source (sensor) for producing exact function executions in the first member. It is also desirable to be able to make the components easily exchangeable in the system without the latter having to be subjected to modification on account of the replacement. It is also desirable to be able to make the system useable for system changes. In some connections it will perhaps be desirable to use simpler and less expensive components than those already in place, or vice versa. The signal transmission will be non-critical and receiving and separating true signals from interference signals will be salient. It is also in some cases advantageous to be able to use known, well-proven communication protocols, even where these are in principle intended for other signal handling, for example prioritizing messages. This concerns in particular those circuits in which the protocol handling is built into hardware, that is existing known systems (for example CAN, SDLC, GPIB, Multibus, and the like) are used in an entirely different way.
In a system where certain events will result in functions in other parts of the system, the signal is normally transmitted directly from the sensor to the unit which will execute the function. Since many events will take place in a machine, this requires a great quantity of conductors, and the unit which delivers the signal on these conductors must take into account the delays which can occur on the way from where the output signal arises to where the desired function is effected.
The new device and the new method according to the present invention are intended to solve the above problems in an advantageous manner.